In the state of the art, contact between the wire ends of the voice coil and the stationary loudspeaker connections are mostly accomplished in such a way, that each bare end of the voice coil wire, i.e. from which baking lacquer and insulation have been removed, is connected to the respective stationary contact point by a connection line. To ensure movement of the diaphragm or the voice coil support, the connection lines between the wire ends of the voice coil and the stationary contact points on the loudspeaker are formed so that they span the lateral distance between the wire ends and the connections in the form of a bow. The bow-shaped course of the connection lines is designed so that a separation remains between the underside of the diaphragm and the connection lines, to prevent the connection lines from touching the diaphragm under the effect of the excursion movements of the oscillating loudspeaker parts.
This requires connection lines which on the one hand are dimensionally stable so as to maintain the bow-shaped course, and on the other exert no, or only a small, effect on the excursion movements of the oscillating loudspeaker parts, in spite of their dimensional stability. Because of the effective excursion movements and the bending forces exerted thereby against the connection lines, it is further necessary for the connection lines to contain a high degree of fatigue strength under reversed bending stresses, if a long loudspeaker service life is to be guaranteed.
Connection lines that fulfill these requirements are made of a woven wire mesh and most often contain a plastic core. Such connection lines are also called stranded loudspeaker conductors.
The connection of these stranded loudspeaker conductors to the wire ends of the voice coil is achieved by soldering. However, this type of connection is not uncritical. If the wire ends of the voice coil are held together with the strands of the connection lines while the soldering takes place, the baking lacquer and the insulation jacket of the wire ends are burned through the effect of the soldering heat, as well as the plastic core of the stranded loudspeaker conductor in the area where the wire ends and the strands are exposed to the soldering heat. Since the stranded loudspeaker conductors are made of woven wire mesh, and are therefore very inclined to accept the solder under the capillary effect, the soldering must be very accurate, i.e. take place within a precisely defined period of time. Even small increases in the soldering time and/or the soldering temperature lead to the burning of large areas of the plastic core, or extra solder is deposited into the stranded conductors, thereby allowing solder to permeate into longer areas of the stranded conductor. The latter results in longer than anticipated areas being solidified by the cooling solder. A further consequence is that under the effect of the excursion movements, the stranded conductors break in the area that was unwontedly permeated by solder.
When the stranded loudspeaker conductors have been conductively attached to the wire ends, the connection area on the diaphragm and/or the voice coil support is additionally protected by means of an adhesive.
The connection of the loudspeaker conductors to the contacts is mostly accomplished as a soldered connection, since soldering is less critical on this side of the conductors because of the fewer bending stresses in that area. It is also known to make the connection between conductor and contact in clamped form, which entirely eliminates any remaining soldering problems.
If loudspeakers must be exposed to more than 250.degree., the technique explained so far can no longer be used. This is so because the safeguard of the adhesive connection between the conductors and the wire ends loosens. The result is that the separating connection areas lead to an all-out malfunction of the loudspeaker, because the wire ends of the voice coil in the separated connection areas are exposed to high bending stresses due to the excursion movements of the oscillating loudspeaker parts, and will quickly break since they are not designed for such loads.
Furthermore, such temperatures create the additional problem of softening of the soldered areas, thus dissolving the connection between the wire end and the conductor.
To solve these problems of high-temperature-affected loudspeakers, an arrangement is known from DE 42 41 12.9, whereby contact of the voice coil wire ends is achieved with a spring arrangement located on the pole body of the loudspeaker, without exposing the voice coil wire ends to bending stresses. With the known arrangement, a soldered connection between the wire ends and the respective contact parts of the spring arrangement can be omitted, if clamping devices are provided on the contact parts, for example.
From DE 44 19 311.4 it is also known to use the conductive segments of a centering diaphragm, which are insulated from the voice coil support to which the voice coil wire ends are routed. The voice coil wire ends are connected to the respective segments of the centering diaphragm by means of ultrasonic welding.
Aside from the fact that the last two arrangements are very costly, they also require production arrangements that deviate considerably from the production lines of conventional loudspeakers comprising bow-shaped connection lines. As before, there is still the need for a connection line and loudspeaker contacts that can withstand over 400.degree. of temperature and can be produced simply, i.e. without vast changes in the conventional production lines.